Tea extraction



ymation of gas pockets.

Patented May 19, 1953 TEA EXTRACTION William R. Johnston, Bronxville,Ismar M. Reich, New York, and Glennard E. Miller, Bronx, N. Y.,assignors to Standard Brands Incorporated, New York, N. Y., acorporation of Delaware No Drawing. Application July 20, 1950, SerialNo. 175,024

4 Claims.

This invention relates to an improved process for preparing a waterextract of tea which may be concentrated or dried. At the properconcentration the product yields a most acceptable tea beverage.

It is customary in the manufacture of such extracts on a commercialscale to pass hot water through columns of tea leaves in the presence ofair. It is difiicult to operate the cylindrical extractors eificientlybecause the air retained by the tea leaves results in the formation ofgas pockets, which tend to reduce or stop the flow of extract or promotexcessive pressure drop in the extractors. Accordingly, the extractorsholding the tea column can be only partially filled with tea leaves andusually only a little over half filled. Furthermore, with air in theextractors there is a tendency for channelling to take place in the teacolumn.

It is possible on a laboratory scale to avoid these difiiculties byoperating in a vacuum as described in U. S. Patent No. 2,235,700. Vacuumoperation on a commercial scale is not practical because of unavoidableair leaks. Through extensive research it has been found that efficientcommercial operation can be efiected by replacing the air in contactwith the tea leaves by carbon dioxide gas prior to extraction. When theextractors are filled with tea and carbon dioxide rather than with teaand air, they can be charged with much more tea, even to the point ofbeing substantially filled without any danger of causing excessivepressure drop. Apparently the water solubility of carbon dioxidepromotes wetting of the tea leaves, thus avoiding the for- Even if notcompletely dissolved in the extract, the carbon dioxide probably canmigrate to the top of the extractor via the wet tea leaves withoutbecoming trapped in pockets as is air, which is substantially insolublein the extract and tends to prevent wetting of the tea leaves. Thewetting effect of carbon dioxide also tends to prevent channelling inthe tea column, thus promoting uniform extraction and higher yields.

In carrying out the invention the air may be removed from the extractorsand replaced with carbon dioxide in any desired manner. For instance,the extractor may be charged with tea leaves, then evacuated and theevacuated extractor charged with carbon dioxide to a pressuresubstantially equal to or higher than atmospheric pressure. Also, theair can be flushed out with a stream of carbon dioxide instead of beingevacuated. It is not necessary that the atmosphere in contact with thetea leaves consist substantially entirely of carbon dioxide becaus goodresults are obtained when it contains as much as 5 to 10 per cent air.

To show the improvements obtained according to the invention, a seriesof extractions were made in a battery of five cylindrical extractorsoperated on the countercurrent principle. In each series the procedureand conditions were identical except that in the first series the chargeof tea leaves was in contact with air at the start of theextractiomwhereas in the other series the extractors were filled withcarbon dioxide before extraction and the charge in each column was 130%to 145% of the charge used in the first series. In the second series theextractors were charged with tea, evacuated to 28 to 29 inches ofmercury gauge vacuum and then filled with carbon dioxide to a gaugepressure of 2 pounds per square inch. In the latter case the averageyield of extractable tea solids was increased to 115% of the yieldobtained in the first series, based in each case on the weight of tealeaves charged. In another run with carbon dioxide an even greateryield, amounting to 130% relative to the first series, was obtained.This yield was obtained using a charge of tea leaves amounting to of thecharge used in the first series.

Tea extraction It is to be understood that when we speak of extractionwith water in the appended claims we intend to include extraction withwater containing added edible substances. For instance, the extractionmay be performed with a tea infusion and with water or a tea infusioncontaining carbohydrates such as corn syrup.

We claim:

1. The process of producing a tea extract which comprises charging anextractor with tea leaves, evacuating air from the extractor, fillingthe evacuated extractor with carbon dioxide and then passing waterthrough said extractor.

2. The process of producing a tea extract which comprises charging anextractor with tea leaves, replacing nearly all of the air therein withcarbon dioxide and then passing water through the extractor.

3. The process of producing a tea extract which comprises charging anextractor with tea 5 leaves, replacing nearly all of the air thereinwith carbon dioxide to a pressure at least equal to atmospheric pressureand then passing water through the extractor.

4. The process of producing a tea extract which comprises extractingwith water a column of tea leaves at a pressure which is at least at- 4mospheric in an ambient atmosphere of carbon dioxide containing not morethan 10% of air.

WILLIAM R. JOHNSTON. ISMAR M. REICH, GLENNARD E. MILLER.

References Cited in the file of this patent UNITED STATES PATENTS 10Number Name Date 1,094,675 Moncrief Apr. 28, 1914 2,235,700 Eidred Mar.18, 1941

1. THE PROCESS OF PRODUCING A TEA EXTRACT WHICH COMPRISES CHARGING ANEXTRACTOR WITH TEA LEAVES, EVACUATING AIR FROM THE EXTRACTOR, FILLINGTHE EVACUATED EXTRACTOR WITH CARBON DIOXIDE AND THEN PASSING WATERTHROUGH SAID EXTRACTOR.